In the sport of ice speed skating, the overwhelming majority of skaters for many years have used a type of skate where the foot retaining portion (i.e., the boot) is fixedly mounted to an elongated blade by forward and rearward pedestals. To use these conventional skates effectively, a skater must learn to maintain his ankle in a rigid position while placing pressure on his heel and pointing his toes skyward to keep the blade parallel to the ice during stride and obtain relatively long strides. However, skating in this fashion restricts the ankle's role in propulsion, virtually omits the power of the ankle and the calf muscles from the stride, and causes the blade to leave the ice before full leg extension is complete. Further, this conventional method of skating causes the leg muscles to be tense through most of the stride, creating a stiff, robotic effect that inhibits optimum performance.
A "clap skate" differs from a conventional skate in that skater's boot is pivotable forwardly with respect to its blade about a pivot axis transverse to the length of the blade. Examples of existing clap skates are shown in FIGS. 1-2, FIG. 3, and in European Patent Application No. 192,312. In clap skates, the forward portion of the boot is pivotally attached to the blade while a rearward portion of the boot can be tilted forwardly as it moves about an established front pivot axis. A pivot and biasing arrangement allows the heel of a skater's boot to rise and fall and biases the blade with respect to the boot, which keeps the blade in contact with the ice for the length of the skater's stride. These pivot and biasing arrangements allow the skater to take longer and more fluid strides, and allows all the leg muscles to work in a fluid, more efficient manner, resulting in an economy of motion and faster skating times.
The separating heel design of the clap skates also allows the skater to add the power of his calf muscles to his stride, while keeping the blade on the ice. In essence, it provides an extra set of muscles for the skater to use. The skater's legs can therefore act more like that of a jumper, who flexes the ankle, pushing off the heel, then the ball of the foot and then the toes. This makes the strides longer and much more powerful.
There are two ways to use clap skates, either of which achieves benefits over the conventional skates. One way is for the skater to sit just as deep as he ordinarily would, but get a longer push. The other alternative is for the skater to sit higher, but get the same push. Sitting higher is advantageous because it almost always results in better endurance.
One prior art clap skate design is shown in FIGS. 1 and 2. Skate 10 includes a boot 12 and a blade 14 which is held in an elongated tubular blade holder 15. The bottom of the boot 12 includes fore and aft mounts 16, 18, respectively. Boot 12 is coupled to an upper frame member 20 by attaching the bottom of mounts 16, 18 to upper frame member 20.
A pair of laterally spaced parallel brackets 22 are attached to blade holder 15. A pin 24 extends through parallel holes in the brackets 22 and a hole in the forward portion of the upper frame member 20. The rearward portion of the upper frame member 20 is not attached to the blade 14 so that the upper frame member 20 and the boot 12 can pivotally move with respect to the blade 14 about the axis of the pin 24. The upper frame member 20 is laterally guided with respect to the blade 14 and blade holder 15 only at its fore end by opposing inner wall surfaces of laterally spaced parallel brackets 22.
On both the lateral and medial sides of the blade 14, a spring 26 is connected at its ends to projections 28, 30 on the parallel brackets 22 and the upper frame member 20 respectively. Springs 26 are pretensioned so that the blade 14 and blade holder 15 are biased towards a closed position as shown in FIG. 1. As the skater flexes his ankle during stride, the boot 12 and upper frame member 20 pivots with respect to the blade 14 and blade holder 15 to move from the closed position, as shown in FIG. 1, to an open position, as shown in FIG. 2. The springs 26 return the blade 14 and blade holder 15 to the closed position when the blade 14 is lifted off the ice. A stop 32 is located on the top of an aft pedestal mount 33 which is attached to the blade holder 15 aft of brackets 22 so that the upper frame member 20 stops in a predetermined position.
Another prior art clap skate design is shown in FIG. 3 and is designated by reference numeral 40. The primary difference between skate 40 of FIG. 3 and skate 10 of FIGS. 1 and 2 is that the coil springs 26 of skate 10 have been eliminated, and a torsional spring 42 has been added adjacent the front pivot axis 44. In addition, in lieu of stop 32, a hollow cone 46 is mounted on the rearward portion of the boot 47 and interfaces with a cone shaped projection 48 mounted to the blade holder 49.
While providing advantages over conventional fixed skates, these and other prior art clap skate designs include a number of drawbacks. Problems and drawbacks exhibited by prior art clap skates are related to the spring biasing systems used and other aspects of the skates. With respect to the spring biasing systems, drawbacks may reside in low return spring rates and/or erratically controlled spring forces. Other problems and drawbacks include poor lateral stability between the boot and blade which can result in excessive and undesirable torques on the hinge and blade, especially during cross-over strides when the skater is going around turns. Further, none of the prior art skate designs provide structure permitting simple adjustment of the biasing force. Moreover, the structural arrangements in the prior art skates that are used to stop the members as the blade moves to the closed position create a single point shock force which is felt by the skater. A few examples of the drawbacks are described below with respect to skates 10 and 40 of FIGS. 1 and 2 and FIG. 3, respectively.
In skate 10 of FIGS. 1 and 2, two springs 26 are used to apply the biasing force to the blade and blade holder to move them to the closed position. However, this design has drawbacks associated with the spring design and interaction with other elements of the skate. As can be seen from FIGS. 1 and 2, the spring forces are directly applied to the upper frame member 20 at projections 30--a point located slightly less than halfway from the pivot axis 24 to the aft end of the upper frame member 20 and also slightly less than halfway from the pivot axis 24 to the connection point between aft boot mount 18 and the upper frame member 20. This feature, in combination with the feature that the upper frame member 20 is laterally guided with respect to the blade 14 and blade holder 15 at its fore end by opposing inner wall surfaces of laterally spaced parallel brackets 22 and at its rear end only during the very end of its pivotal motion towards its closed position by opposing side surfaces of stop 32, causes high lateral torsional forces to be applied at the hinge, i.e., pin 16 and laterally spaced parallel brackets 22, whenever the force applied to the upper frame member 20 by the skater is not exactly coincident with blade 14. These lateral forces are undesirable because they cause the aft end of the upper frame member 20 to be laterally displaced from the longitudinal axis of the blade 14 causing inefficient transfer of the skater's thrusting force to the blade and poor lateral stability. It may also lead to damage of the laterally spaced parallel brackets 22 or the pin 24. Moreover, these undesirable forces are the highest at the most critical times of race, when the skater is going around turns and crossing-over--where the races are most often won and lost.
Another drawback in this design is that the connection points between the ends of the springs 26 do not take full advantage of the length that the spring could theoretically extend. This results in a low spring return rate and/or the use of unnecessarily large springs. Further, there is no way for the skater to adjust the spring return rate without having to replace the spring. This is undesirable because skaters would have to carry a collection of springs if they wanted to gain a competitive advantage by adjusting the spring return rate due to conditions of the ice surface.
Yet another drawback of this design is that two springs are required to produce a balanced biasing force along the longitudinal axis of the blade. Further, as the springs are medially and laterally spaced from the central longitudinal axis of the blade, their inherent positioning exposes the springs and makes them especially susceptible to physical damage in use and in transportation.
In the design as shown in FIG. 1, when the blade 14 is in the closed position, the skater's thrust force is transferred to the blade 14 and blade holder 15 in only two small areas--at the hinge and at the stop 32. This results in the skater's thrust force being transferred at high and possibly uneven concentrations. Moreover, because stop 32 includes only a small surface to apply the stopping force, this stopping force is highly concentrated. This can lead to repetitive shock forces being absorbed by the skater on his heel and a louder distracting clapping force generated each time the blade 14 and blade holder 15 moves to their closed position.
Skate 40 of FIG. 3 includes many of the same or similar drawbacks and exhibits many of the same or similar undesirable qualities as skate 10 shown in FIGS. 1 and 2. Spring 42 of skate 40 applies the biasing force to the blade and blade holder to move them to the closed position. However, the spring force is applied immediately adjacent the pivot pin by torsion spring 42. This results in undesirable lateral torsional forces which are even greater that those of skate 10 of FIGS. 1 and 2 because the biasing force is applied at or immediately adjacent the hinge pin.44. As described above, this can cause inefficient transfer of the skater's thrusting force to the blade and poor lateral stability, and it may also lead to damage of the laterally spaced parallel brackets 22 or the pin 24. Further, the torsional spring 42 does not take full advantage of the length that the spring could theoretically extend. There is also apparently no way for the skater to adjust the spring return rate without having to replace the spring. Skate 40 is also similar to skate 10, in that the skater's thrust force is transferred to the blade 14 and blade holder 15 in only two small areas resulting in the skater's thrust force being transferred at high and possibly uneven concentrations, and a highly concentrated stopping force.